Composite Propeller Blade Spar Retention via Segmented Weaving
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Solution Overview
Problem
Propeller blades for turboprops face challenges in maintaining the positioning of the shaping portion of the spar within the fiber structure, especially under mechanical stresses, due to the presence of non-interlinked zones which can lead to instability at the rear edge of reduced strength.
Innovation Solution
The design incorporates a streamlined fiber reinforcement structure with a non-interlinked zone forming a housing for the spar, featuring a retaining portion at the rear edge that extends less than the housing height, ensuring the spar remains in position, and a method involving three-dimensional weaving and matrix densification to enhance mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a non-interlinked zone is provided inside the fiber structure to form a housing for the shaping portion of the spar, then the spar can be inserted into the fiber structure, but the mechanical strength of the fiber structure is reduced, especially at the rear edge
Solution Approach 1:
The non-interlinked zone is segmented into two functional parts: an opening portion that allows insertion of the shaping portion of the spar, and a retaining portion that maintains mechanical strength. This segmentation enables the structure to simultaneously achieve ease of insertion and maintain strength by distributing the non-interlinked zone across different functional zones.
Solution Approach 2:
The fiber structure is designed with different local qualities: the opening portion has reduced interlinking to facilitate insertion, while the retaining portion maintains full interlinking to preserve mechanical strength. This local differentiation allows the structure to optimize both insertion capability and strength in different regions.
2Ease of operation
If the opening in the rear edge extends over the full height of the housing, then the shaping portion can be easily inserted, but the retaining portion is compromised and the spar may move under mechanical stress
Solution Approach 1:
Instead of providing a full-height opening that would maximize ease of insertion, the design uses a partial opening that extends over only part of the housing height. This partial action is sufficient for insertion while leaving the retaining portion intact, thereby achieving a balance between ease of operation and positioning stability.
Solution Approach 2:
The opening is segmented vertically into an insertion zone and a retaining zone. The insertion zone provides access for the shaping portion, while the retaining zone maintains structural integrity. This vertical segmentation allows the opening to serve its insertion function without compromising the retaining portion's ability to hold the spar in position.
3Device complexity
If the fiber structure is made as a single piece by three-dimensional weaving, then manufacturing complexity is reduced, but the ability to provide both opening and retaining portion is limited
Solution Approach 1:
The non-interlinked zone is formed during the three-dimensional weaving process itself, before the fiber structure is completed. By incorporating the opening and retaining portion design into the weaving process, the structure achieves complex functionality without requiring additional manufacturing steps or assembly operations.
Solution Approach 2:
The opening portion and retaining portion are merged into a single integrated non-interlinked zone within the three-dimensionally woven fiber structure. This merging allows both functional elements to be achieved through one manufacturing process, maintaining manufacturing simplicity while providing structural versatility.
Data Source
AI summary
An aircraft propeller blade including a streamlined structure constituted by at least one piece of fiber reinforcement obtained by three-dimensionally weaving yarns and densified by a matrix, together with a spar including an enlarged portion extending outside the fiber reinforcement and forming the root of the blade, and a shaping portion present in a housing arranged inside the fiber reinforcement. The fiber reinforcement includes a non-interlinked zone forming the housing inside the fiber reinforcement. The non-interlinked zone opens out into the bottom portion and into the rear edge of the fiber reinforcement so as to form an opening for inserting the shaping portion of the spar into the housing of the fiber reinforcement. The opening present in the rear edge of the fiber reinforcement extends over a height that is less than the height of the housing.